Communication between the one or more implantable medical devices (IMDs) and an external programmer may be facilitated by conductive communication via patient tissue. The use of conductive communication of information provides certain improvements over more conventional communication techniques. For example, conductive communication techniques enable communication without requiring a programmer head be held undesirably close to a patient or to be held in a precise position relative to an implant site for an extended period of time. Conductive communication also enables power consumption to be reduced due to substantially lower current requirements and eliminating peak power demands currently imposed by existing inductive and radio frequency (RF) communication techniques. This can beneficially extend the life of an IMD. Also, conductive communication techniques use elements generally already existing in an IMD, such as the therapeutic electrodes that function as an input-output device, enabling elimination of a coil or antenna that are conventionally used for inductive and RF communication and reducing complexity and component count significantly.
In order to perform conductive communication, at least two programmer skin electrodes (that are part of or coupled to an external programmer) are attached to skin of a patient in whom one or more IMDs is/are implanted, and the programmer skin electrodes are used to transmit information to and/or receive information from the IMD(s) via conduction through body tissue of the patient. One potential problem with using conductive communication is that the orientation of the IMD(s) can cause fading that can adversely affect both programmer-to-implant (p2i) communication and implant-to-programmer (i2p) communication. More specifically, certain orientations of an IMD may cause conductive communication to be intermittent or stop completely, which may occur when an electric potential field generated between programmer skin electrodes has too small a difference between the electrodes of the IMD. It is often impractical to mitigate such fading by changing the orientation of an IMD and/or the placement of its electrodes, since the orientation of the IMD and/or the placement of its electrodes is already severely constrained by mechanical requirements and implant-to-implant (i2i) communication requirements. Further, where the programmer skin electrodes are also being used to sense an electrocardiogram (ECG), which is often the case, it may be impractical to mitigate such fading by changing the placement of the programmer skin electrodes since the placement of such electrodes is often fixed or at least constrained by ECG requirements.